A Mechanical-Modulated-Flux HIA with Permanent-Magnet-Iron Modulator Used for Flywheel Energy Storage System

As a new type of energy storage motor, the mechanically-modulation-flux energy storage homopolar inductor alternator (HIA) has the advantage of high reliability and low idle loss and can be applied to energy storage systems in power systems. At present, the existing mechanically-modulation-flux energy storage HIA have gaps between the modulation ring and the motor housing, and the magnetic electromotive force of the main magnetic circuit of the motor cannot be completely short circuited by the modulation ring. Therefore, under idle operating conditions, the magnetic flux density of the main air gap cannot be reduced to zero when the motor is unloaded, and there is still no-load iron loss in the motor, which limits the further improvement of the energy storage system efficiency. This paper proposes a magnetic modulation ring structure with permanent magnets and optimization method for an energy-storage HIA. By optimizing the size of the modulation ring and selecting the optimal outer diameter of the modulation ring, theoretically, the main air gap magnetic density of the motor can be reduced to zero. Therefore, the no-load loss of the motor under idle conditions is almost zero, which can greatly improve the efficiency of energy storage systems based on HIA and is very suitable for application in power system energy storage. This article analyzes the optimization design method for the size of the modulation ring. Finally, the excellent magnetic field regulation performance of the motor was verified through finite element simulation.